A 79-year-old woman without significant medical or surgical history was referred to our hospital complaining of a slowly growing anterior neck swelling. She stated that this swelling started to appear in her neck 6 months ago. The swelling was painless and gradually increasing in size. She refused to seek medical advice throughout those months till she started to feel some respiratory discomfort.

Clinical examination revealed a stony hard neck swelling that moved up and down with deglutition, mostly of thyroid origin. The swelling was not tender and its lower border could not be felt by palpation, denoting the possibility of retrosternal extension (Fig. 1A).

Fig. 1
figure 1

A Preoperative photo showing the thyroid swelling with undefined lower border. B Postoperative photo of the resected thyroid gland showing replaced right lobe by large hard nodule

Neck ultrasonography showed a nodule in the lower pole of the right thyroid lobe. This nodule was hypoechoic with internal vascularity, microcalcification, and cystic degeneration measuring about 3–4 cm. It was categorized as TIRADS 4b [3]. It extended down to the mediastinum with some enlarged cervical lymph nodes with preserved criteria.

Computerized tomography scan with contrast of the neck and chest was done and revealed a soft tissue mass measuring 3.3×4.8 cm inseparable from the right thyroid lobe, contacting strap muscles anteriorly and prevertebral muscles posteriorly, compressing and displacing trachea to the left side, contacting the right carotid sheath with neither encasement nor infiltration. The mass was extending inferiorly to the mediastinum and left brachiocephalic arch and reaching the level of the fifth cervical vertebra (Fig. 2). Few nodules were seen in both lung fields; the largest was measuring 5 mm in the left anterior segment of the left lung for follow-up.

Fig. 2
figure 2

Post-contrast neck and upper chest CT axial (A, B) and coronal images (C). Heterogenous enhancing right thyroid lobe soft tissue mass with coarse calcification is seen displacing the airway to the contralateral side and extending down to the superior mediastinum abutting the aortic arch branches with clear fat plane in-between. It was seen also contacting the right CCA along its length without vascular invasion (arrows). No pathological cervical LNs

Thyroid function tests were of normal values and her vocal cords were freely mobile bilaterally.

FNAC was taken from the hard thyroid swelling. Smears prepared were moderately cellular showing occasional scattered groups of cells with a moderate degree of atypia and pleomorphism in RBCs background, categorized as Besthesda V [4].

The patient was prepared for surgery after a multidisciplinary discussion. Total thyroidectomy was done, visualizing both recurrent laryngeal nerves and preserving the parathyroid glands. The surgery was adopted via a fully cervical approach “Kocher’s collar incision” without sternotomy. The patient had a smooth postoperative course and was discharged 48 h after surgery.

The right lobe measured 8×8×4 cm and the left lobe measured 4×3×2 cm. Dissection of the right lobe revealed a tissue nodule measuring 6×5×4 cm. It had hard cut surface, whitish alternating with yellowish areas. The left lobe showed a nodular glistening brownish cut surface (Fig. 1B).

Sections prepared from the right lobe revealed infiltration by well-circumscribed lobulated malignant tumoral proliferation formed of cartilaginous matrix with chondrocytes embedded in lacunae and showing hypercellularity, occasional binucleate nuclei and scarce mitosis. Foci of myxoid degeneration were also seen. No detected necrosis. Focal bone formation was detected. Sections from the left lobe and isthmus were free. Slides stained for cytokeratin, EMA, P63, TTF1, Pax8, and thyroglobulin were negative in the tumor cells (Fig. 3). Ki-67 was less than 5% which is against high ki-67 proliferation index usually seen in anaplastic thyroid carcinoma. Picture of low-grade chondrosarcoma of right thyroid lobe was the final pathologic diagnosis.

Fig. 3
figure 3

A Tumor formed of lobules of malignant chondrocytes embedded in a chondroid matrix and separated by fibrous septa, H&E 100×. B Tumor cells were negative for thyroglobulin in contrast to entrapped thyroid follicles which were positive for thyroglobulin 200×. C Tumor cells were negative for TTF-1, 400×. D Tumor cells were negative for PAX-8, 400×. E Tumor cells were negative for CK, 400×

Comprehensive immunohistochemical studies showed that this tumor is not consistent with anaplastic thyroid carcinoma with chondrosarcomatous differentiation as the tumor cells were totally negative for TTF-1, thyroglobulin, and PAX-8 which are the major three markers used in immunohistochemical studies for the determination of thyroid origin. In addition, tumor cells were completely negative for panCK, CK7, CK20, EMA, and P63. Lastly Ki-67 was less than 5% which is against high ki-67 proliferation index usually seen in anaplastic thyroid carcinoma. These findings were all supportive for the diagnosis of low grade chondrosarcoma

The possibility of metastatic chondrosarcoma to the thyroid gland was ruled out by a computerized scan of the whole body’s skeleton that did not detect any primary tumor. MDT discussion agreed for active surveillance of the patient on levothyroxine replacement therapy.

Six months postoperative, the patient was in a good general condition; her follow-up CT examination revealed clear operative bed, with calcified paratracheal nodes measuring about 8×10 mm. Bilateral multiple calcified pulmonary nodules were also detected; the largest was in the left upper lung lobe measuring 8×7 mm possibly metastatic regarding the patient’s history.

A computerized scan of the chest 18 months postoperative revealed a progressive course of the pulmonary nodules reaching a size of 25mm with moderate right-sided pleural effusion that was proved to be malignant by cytological evaluation. At that time the patient’s performance declined to ECOG 3. That is why the multi-disciplinary tumor board recommended best supportive care and pain therapy measures.

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